1. Field of the Invention
This invention relates to a chuck device, for example, a chuck device which is fixed to an extreme end of an arm of an industrial robot, holds a workpiece and be applied for its transportation or assembly or the like.
2. Description of the Prior Art
As a prior art chuck device, as shown in Jap.Pat.Laid-Open No.Sho 60-52282, a rack is connected to a rod of a driving source such as a reciprocating cylinder or the like and further a pair of pinions are engaged with the rack and then each of holding claws can be opened or closed to their maximum degrees of opening by arms extending from the pinions.
However, this type of chuck device is used, for example, as shown in FIG. 10, in an automatic parts feeding operation in such a way as each of holding claws 102 and 102 is fixed to a pair of right and left arms 101 and 101 driven to be opened or closed, a workpiece 103 such as an electronic parts or the like is held and at the same time a cylinder 104 fixed to the chuck device similarly depresses the workpiece 103 through a pushing rod 106 resiliently supported by a spring 105, a leg part 103a of the parts is inserted into a fixing hole 107a of a printed circuit board 107, thereafter each of the arms 101 and 101 as well as the holding claws 102 and 102 is widely opened and then an entire chuck device is pulled up.
In this case, before holding the workpiece 103, it is preferable to have the maximum degree of opening of the chuck as much as possible so as to enable the positive holding of the workpiece to be carried out even if the position where the workpiece 103 is mounted is slightly displaced. In addition, it is also preferable that when the chuck is to be released from the workpiece 103, a degree of opening of the chuck is made as less as possible in so as to prevent other adjoining electronic parts already inserted into the printed circuit board 107 from being deformed or damaged.
However, in case of the prior art chuck device described above, since the chuck is opened to its maximum degree of opening even in case of releasing the workpiece, the prior art chuck device may not be adapted for a printed circuit board having several electronic parts closely gathered to each other on it due to the aforesaid reasons. If a surplus space is provided in case of using this type of chuck irrespective of this size, a printed circuit board design becomes out of its normal standard one to cause a troublesome operation and further it may generate some problems such as an increased size of the printed circuit board or a large-sized entire device having the printed circuit board assembled therein.
In turn, if the degree of opening is low, it is not possible to hold a large-sized workpiece and if the degree of opening is too much, an operation to hold or release a small workpiece may generate an useless state to cause a working efficiency to be decreased.
In view of the above, the present invention may resolve these problems and it is an object of the present invention to provide a chuck device which can be used even at an intermediate degree of opening in addition to its maximum degree of opening.